Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

Question # 1

Define power and explain its units

Ans 1: Power is defined as the rate of doing work.
Mathematically:
Power=P= work done / time taken
P=W/t
Ans 2: Quantity: work is a scaler quantity. Therefore , power is also a scaler quantity.
Ans 3: Unit: SI unit of power is watt(W)
Ans 4: Watt: the power of a body is one watt if it does work at the rate of 1 joule per second ( 1 Js^-1)
Formula:
1W = 1j / 1s
Ans 5: Bigger units : bigger units of power are kilowatt , megawatt etc
1KW=1000W=10³W
!MW=1000000W=10⁶W
1hp=746W

Question # 2

How is energy converted from one form to another? Give some examples

Ans 1: Interconversion of energy: the conversion of one form of energy into another form is called interconversion of energy.
Explanation: energy cannot be destroyed however it can be converted into some other forms . For example, rub your hands together quickly. You will feel them warm. You have used your muscular energy in rubbing hands as a result heat is produced. In the process of rubbing mechanical energy is converted into heat energy. Processes in nature are the results of energy changes. For examples, some of the heat from the sun is taken up by water in the oceans. This increases thermal energy. Thermal energy causes water to evaporate from the surface to form water vapors. These vapors rise up and form clouds. As they cool down, they form water drops and fall down as rain. Potential energy changes to kinetic energy as the rain falls . This rain water may reach a lake or a dam. As the rain water flows down, its kinetic energy changes into thermal energy while parts of kinetic energy of flowing water is used to wash away soil particles of rocks known as soil erosion. During the interconversion of energy from one form to other forms, the total energy at any time remains constant .

Question # 3

Define work. when a force do work? explain

Ans 1: Work: work is said to be done when a force acts on a body and moves it in the direction of the force.
Recognition of work: the question raised how much work is done? naturally, greater is the force acting on a body longer is the distance moved by it, larger would be work done
" work is done when a force acting on a body displaces it in the direction of force".
Ans 2: Quantity: work is scaler quantity
Ans 3: Dependence; it depends on the force acting on the body, displacement of the body and angle between them.
Ans 4: unit: its unit is joule(J)
Ans 5: Definition: if one newton force act on the body it covers one meter distance in the direction of force, then its work will be one joule
1J= 1N*1m

Question # 4

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Ans 1: m= 50 kg
Height of h= 16 cm
each step = 0.16m
n= 25
t = 20s
p= ?
Since
F = w
= mg
= 50 x 10
= 500N
Height = h= 0.16 x 25 = 4m
reached by man
As we know that
P =w/t = F x s/t
By putting the values
P= 500 x y/20
= 2000/20
= 100w Ans

Question # 5

Q no: 6(A) Define efficiency. Write its formula.

Ans 1: Efficiency:
Efficiency of a system is the ratio of required form of energy obtained from a system as output to the total energy given to it as input.
Example:
Electric motors may be used to pump water, to blow air , to wash clothes, to drill holes, etc for that they use electricenergy. How good a machine is depends how much output we obtain from it by giving certain input .The ratio of useful output to input energy is very important to judge the working of machine
Mathematical form:
Efficiency =Required form of output/Total input energy x100

Question # 6

Write a note on energy a nd environment

Ans 1: Sources; environmental problems such as pollution that consist of noise , air pollution and water pollution may arise by using different sources of energy such as:
- Fossil fuels
- Nuclear energy
Ans 2: Pollution: polliton is the change in quality of environment that can be harmful and unpleasent for living things.
Thermal pollution: a temperature rise into the environment that disturbs life is called thermal pollution.
Effects:
- Thermal pollution upsets the balance of life.
- It endangers the survival of many species
Ans 3: Air pollutants: Air pollutants are unwanted and harmful. Natural processes such as volcanic eruptions, forest fires and dust storm add pollutant to the air. These pollutants rarely build up to harmful levels. On the other hand the burning fuel and solid wastes in homes, automobiles' and factories release harmful amount of air pollutants
Ans 4: Pollution from fission plans: al power plants produce waste heat, but fission plants produce the most. The heat released into a lake , a river , or an oven upsets the balance of life in them. Unlike other power plants , nuclear power plants don't produce carbon dioxide. But they do produce dangerous radioactive wastes.
Ans 5: Laws; in many countries government have passed laws to control air pollution. Some of these limit the amount of pollution that power plants , factories ad automobiles are allowed to give off. To meet this condition for automobiles , new cars have catalytic converts. These devices convert some polluting gases. The use of lead free petrol has greatly reduced the amount of lead in the air. Engineers are working to improve new kinds of car engines that use electricity or energy sources other than diesel and petrol. Many individual communities have laws which protect their areas from pollution. Individuals can help to control arir pollution simply y reducing the use of card and other machines that burn fuel. Sharing rides and using public transportation ar the way to reduce the number of automobile's in use.

Question # 7

Define energy and explain kinetic energy

Ans 1: Energy: the capability of doing work is called energy. A body is capable to do work only when it has energy.
Ans 2: Kinetic energy: the energy of a body due to its motion is called its kinetic energy. This type of energy is possessed by flowing water and fired bullet.
Explanation: the general formula for the calculation of kinetic energy is derived by considering the special case. Consider a ball moving on the ground. If the initial velocity of ball is denoted by vi and its mass m, while moving the ball experiences deceleration( negative acceleration) due to frictional force(-F), roughness of ground and air drag. Ultimately this ball stops, after covering certain distance (S).

Question # 8

Q no: 7(A) Write is the uses of Wind Energy.?

Ans 1: Wind Energy:
Wind energy has used as a source of energy for centuries. It has powered sailing ships across the oceans . It has been used by windmills to grind grain and pump water. More recently , wind power is used to turn wind turbines. When many wind machines are grouped together on wind farms , they can generate enough power to operate a power plant. In the United stated , some wind farms generate more than 1300 MW of electricity a day. In Europe, many wind farms routinely generate hundred megawatts or more electricitya day

Question # 9

What are nuclear fuels? explain it

Ans 1: nuclear fuels: the materials through which we can obtain nuclear energy are called nuclear fuels e.eg uranium element. In nuclear power plants wee get energy as a result of fission reactions.
Ans 2: Nuclear fission reaction: the process in which heavy nucleus breaks into two smaller nuclei releasing a loti of energy is called nuclear fission reaction. During fission reaction, heavy atoms splits into two smaller parts releasing large amount of energy.
Ans 3: Example: fission reaction of uranium element
Ans 4: Uses: nuclear power plants give out a lot of nuclear radiations and a vast amount of heat. A part of this heat is used to run power plants while a lot of heat goes waste into environment

Question # 10

Explain different kind of energy

Ans 1: Types of energy: there are number of forms of energy.
- Mechanical energy: the energy of a body both due to its position or due to its motion is called the mechanical energy e.g.wind ,water running down in stream etc. possess mechanical energy.
- Heat energy: The energy obtained due to burning of fuel is called heat energy. it obtained from the sun, or from the electric energy. It may also be obtained by burning of fuel. The main source of heat is the sun.
Ans 2:
- Electrical energy: the energy due to flowing charges is called electrical energy. It is obtained from batteries and generators. It is used to run electric lamps, household appliance.
- Sound energy: energy carried by sound waves is called sound energy. The sound waves are mechanical waves. These are produced by vibrating bodies. e.g, vibrating string and flute
Ans 3:
- Light energy: Light consists of electromagnetic waves, which posses energy it is called " light energy". The main source of light energy is the sun. it is also obtained by burning candles, bulbs, fluorescent tubes and burning fuel.
- Chemical energy: there are chemical reactions which produce energy. It is called chemical energy. the electrical energy obtained from batteries is due to chemical reactions inside batteries e.g, burning of coal, natural gas and wood in air is chemical reaction which release energy as heat and light
Ans 4: Nuclear energy: due to nuclear reactions energy is obtained called nuclear energy. The most famous nuclear reactions are "fission" and Fusion". Fusion nuclear reactions take place in the sun. The nuclear energy is obtained in the form of heat.

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Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

9th Class English Medium Subjects

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Online Long Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Physics (New Book) - 9th Class Physics Chapter 6 Long Question Preparation

Define power and explain its units

How is energy converted from one form to another? Give some examples

Define work. when a force do work? explain

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Q no: 6(A) Define efficiency. Write its formula.

Write a note on energy a nd environment

Define energy and explain kinetic energy

Q no: 7(A) Write is the uses of Wind Energy.?

What are nuclear fuels? explain it

Explain different kind of energy

Prepare Complete Set Wise Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Set 1

Set 2

9th Class Physics Chapter 6 Long Question Preparation - Set 1

Define power and explain its units

How is energy converted from one form to another? Give some examples

Define work. when a force do work? explain

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Q no: 6(A) Define efficiency. Write its formula.

Write a note on energy a nd environment

Define energy and explain kinetic energy

Q no: 7(A) Write is the uses of Wind Energy.?

What are nuclear fuels? explain it

Explain different kind of energy

9th Class Physics Chapter 6 Long Question Preparation - Set 2

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Q no:7 (B) Define Kinetic energy. Derive its formula K.E =1/2 mv²

What are nuclear fuels? explain it

How is energy converted from one form to another? Give some examples

Write and explain energy conversion processes involved in producing of electricity

What is energy converter ?

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

Write note on solar house heating and solar cells

Define power and explain its units

Q no: 6(A) Define efficiency. Write its formula.

9th class Physics Chapter 6 Long Q's (English Medium)

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